Epoxy Board Ready for Hotcoat Questions...

  1. After the lam coat, sand, blow air off, denatured alcohol wipe? Is rubbing alcohol the same? How about Kokua’s recipe for a bubble bath??

  2. Air pin bubbles - I apply epoxy resin hotcoat, it looks great but after 15 minutes dozens of little pin bubbles form. How do I get rid of this??


The dozens - maybe even hundreds - of little bubbles & fisheyes are the big challenge with epoxy hotcoats.

Apparently, Additive F helps solve this by increasing surface tension among the epoxy molecules when brushed on thin? I don’t know, I haven’t used it.

With or without Add F, some things can always lead to this kind of trouble:

  1. dust, oil from your hands, leftover solvents or cleaning supplies, or other contamination

  2. brushing it on too thin - as it seeks its own level it stretches as it runs off & leaves voids

  3. a lam that took too long to set & drained into the foam and left you with lots of pinholes in the lam…and then you hotcoated in a rising temperature and the blank was blowing expanding air out through the lam

  4. too cold / too humid / wrong ratio - your hotcoat takes too long to set & drains off, thinning as it goes

  5. you sanded the lam too smooth & its been several days or more since you did it, and again the hotcoat is draining off

How to fix these problems?

  1. I’ve been washing my lams with Trader Joe’s Citrus Based Organic Shampoo. Cleans off any epoxy setting residue, shop dust, sanding dust, hand oil, etc. and then rinses clean. Starting with the rinse, its all rubber gloves, all the time.

  2. Be generous with the hotcoat. If you run low, don’t brush it around more, just mix another little batch.

  3. Either seal your blank or lam in warmer - but falling - temperatures. Hotcoat in falling temperatures too, so, if anything, the blank is inhaling not exhaling.

  4. Warm up your resin, your garage, use a faster hardener, use a vac bag, use Add F, use a hotbox, etc.

  5. Rough up the lam with 80 or 100 grit and wash it again

or 6. cheat: Hotcoat with poly UV sanding resin. Did that on my fish & it came out perfect…:slight_smile:

Sounds to me like your laminate was too dry. If this was a urethane blank then you probably sqeegeed it to dry. If it was EPS and you didn’t seal then you had some draining. If this was EPS and you did seal then you again sqeegeed too dry. To fix this in the future you can:

  1. seal the blank. This is easy to do and eliminates this problem 95% of the time.

  2. Do a “cheater” coat when the laminate resin is tacky on the surface. This only takes 3 oz. of resin sqeegeed across the flats. Takes like 5 minutes to do and is pretty fool proof. We do this on every EPS board that is NOT sealed. And on some urethanes as well.

  3. leave the laminate very wet.

Hmmm Greg tell me more about the cheater coat. I presume as the laminate is still tacky it helps pull the new resin into any small voids. At what stage do you put the new resin on and is it just a light squeege or do you use a lot of pressure to squeeze it in to any holes, do you pull off the exess?

I usually put the filler coat on about after the lam has gone off then I warm the fresh sanding coat with a heat gun. I thought that by doing this any air expands and pushes out of the lam and as I take the heat away it cools and sucks resin into any holes.

The cheater is done when the resin is tacky because it’s still wet enough to get the resin into the holes. Everything will still move a bit. After its hard it still works but not as well or as easy. I use a lot of pressure with a very stiff sqeegee and try to use the right amount of resin so there is very little excess. If you do have a bit of excess it can be sqeegeed off the rail or sopped up with scrap glass.